Glutathione-Dependent Detoxifying Enzymes in Rainbow Trout Liver: Search for Specific Biochemical Markers of Chemical Stress

Abstract

Abstract-Activities of trout liver microsomal glutathione S-transferase (GST) and a series of cytosolic glutathione-dependent detoxifying enzymes were determined after a single intraperitoneal treatment with phenobarbital, 2,2-bis (p-chlorophenyl)-1,1-dichloroethane (p,pЈ-DDE), 2,3,-dimethoxynaphthoquinone (NQ), or 2, 3,7,. This study aimed to find xenobiotic-specific parameters applicable as biochemical markers of the impacts of the prototypal xenobiotics. The effects of xenobiotics on cytosolic GST activities were substrate dependent. The rate of conjugation of p-nitrobenzyl chloride was significantly induced by higher doses of p,pЈ-DDE or NQ. The conjugation of ethacrynic acid was enhanced by phenobarbital, p,pЈ-DDE, and NQ (i.e., by xenobiotics that do not induce cytochrome P4501A forms). The GST activity against 1,2-epoxy-3-(p-nitrophenoxy)propane was induced only by phenobarbital and by lower doses of p,pЈ-DDE. The cytosolic GST activity, measured with 1-chloro-2,4-dinitrobenzene as a substrate, was only weakly increased by phenobarbital, TCDD, higher doses of p,pЈ-DDE, or by NQ at the lowest dose of 1 mg/kg. Although the latter activity is frequently used as a biomarker in ecotoxicology, various factors (including its weak inducibility) indicate that this biochemical parameter is probably not a suitable indicator of contamination in fish. Similarly, cytosolic glutathione peroxidase was not affected by the prototypal xenobiotics and appeared to be an unsuitable bioindicator of oxidative impacts of the tested compounds. On the other hand, microsomal GST activity was nonspecifically increased by phenobarbital, NQ, TCDD, and high doses of p,pЈ-DDE. Glutathione reductase, another potential biomarker of oxidative stress, was induced by phenobarbital, NQ, and, to a lesser extent, p,pЈ-DDE; therefore it appeared to be a less sensitive indicator to the exposure to prototypal xenobiotics than the microsomal GST. We conclude that the increase of microsomal GST and cytosolic glutathione reductase activities could become useful biochemical markers of oxidative stress, while the induction of cytosolic GST activities toward ethacrynic acid and probably also toward p-nitrobenzyl chloride appear to hold promise as biochemical markers of specific impacts of p,pЈ-DDE and redox cycling quinones in trout liver.

The use of biomarkers in the antioxidant responses ofDaphnia magnato the acute and chronic exposure to no. 20 diesel oil and 2,4-dichlorophenol

“…Decreased GR activity may lead to GSH depletion if the depletion cannot be corrected by the synthesis of new glutathione molecules. Hepatic GR was increased in rainbow trout after a short-term exposure to Phenobarbital, p,p 0 -dichlorodiphenyldichloroethylene (DDE), or the prototypal oxidation -reduction cycling compound 2,3-dimethoxynaphthoquinone (Petřivalský et al, 1997). The mechanism of regulation of GR in organism is still unclear, and the increase in its activity can be interpreted as an adaptive response to oxidative stress.…”

Antioxidant response ofDaphnia magnaexposed to no. 20 diesel oil

“…Considering its importance in defense against toxic effects of xenobiotics, GR has received much attention in biomonitoring studies. In one study, hepatic GR was increased in rainbow trout after a short-term exposure to Phenobarbital, p,p′-dichlorodiphenyldichloroethylene (DDE), or the prototypal oxidation-reduction cycling compound 2,3-dimethoxynaphthoquinone (Petrivalsky et al, 1997). The mechanism of regulation of GR in Daphnia magna is still unclear, and the increase in its activity can be interpreted as an adaptive response to oxidative stress.…”

Influence of season and pollution on the antioxidant defenses of the cichlid fish acará (Geophagus brasiliensis)

“…Nevertheless, although reduced glutathione peroxidase (25,30) and glutathione reductase (25) activities were found in fish exposed to environmental pollution, both enzymes in general showed induced activities in the liver (7,28,31). These Acute and subchronic exposure to pollutants seems to increase reduced glutathione contents in fish cells (26,(32)(33)(34) while fish submitted to heavy and extensive chronic exposure seem to be unable to maintain high constitutive glutathione and total glutathione levels (11,28; Wilhelm Filho D, Torres MA, Testa CP and Tribess TB, unpublished results; present study). The decrease observed both in reduced and oxidized glutathione concentrations may be attributable to the decrease in total glutathione.…”

“…Although some studies have shown induction of SOD (27,28) and other antioxidants (27) or biotransformation enzymes (27,28,31) under pollution exposure, unaltered or lowered SOD activities have been also found in other fish species (7,32). GST, together with EROD activity, is usually enhanced after exposure to different types of organic pollutants, both in laboratory studies (e.g., 31,34) and in field studies (27,31). They represent a complex system related to xenobiotic biotransformation (phase I) and conjugation and excretion (phase II), consisting of prospective biochemical markers of environmental contamination by organic compounds such as polycyclic aromatic hydrocarbons and polychlorinated biphenyls (36).…”